Chapter 9 - Solving Quadratic Equations - 9.2 - Solving Quadratic Equations by Graphing - Exercises - Page 494: 7

$x=-4$

The given equation is $x^2+8x+16=0$ From the given graph. The $x-$intercept is $-4$. Check $x=-4$. $\Rightarrow x^2+8x+16=0$ $\Rightarrow (-4)^2+8(-4)+16=0$ $\Rightarrow 16-32+16=0$ $\Rightarrow 32-32=0$ $\Rightarrow 0=0$ True. Hence, the solution is $x=-4$.